JPH0224603A - Color filters for liquid crystal panels and liquid crystal devices - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color filter (hereinafter abbreviated as CF) used for full-color or multi-color displays.

[Conventional technology]

For the purpose of colorizing liquid crystal displays, plasma displays, etc., a method is generally adopted in which a CF is arranged inside a display panel.

Although various structures of these conventional CFs have been proposed, the one generally used in recent years is a CF made by a manufacturing method called a relief dyeing method.

Relief dyeing is a process in which a dyeable transparent resin such as gelatin is applied onto a transparent substrate, developed and exposed to light using a photomask to form a transparent resin into a predetermined pattern. This is a method of dyeing with dyes such as acid dyes.

By repeating the above steps, it is possible to obtain a CF consisting of dyed parts of red, green, blue, black, etc.

[Problem to be solved by the invention]

When manufacturing a liquid crystal panel using CF manufactured by the relief dyeing method as described above, transparent electrodes for driving the liquid crystal are formed between 1) the dyed layer and the transparent substrate, and 2) the transparent electrodes formed between the dyed layer and the transparent substrate. There are two ways in which it can be formed on the top.

In case 1), the liquid crystal panel has the configuration shown in Figure 2, and the equivalent circuit of the liquid crystal panel is as shown in Figure 3. Therefore, a driving voltage V is applied between the transparent electrodes of the upper and lower substrates of the liquid crystal panel. Even though
The actual voltage VLC applied to the liquid crystal is V LC = (Ccr/C+, c+ Ccp) V, and due to the effect of this voltage drop, the driving voltage is (CLC + CCF/CCF) times as much as that of a conventional liquid crystal panel. It is necessary to apply

The rate of increase in this drive voltage is determined by the thickness of the liquid crystal layer, the dielectric constant of the liquid crystal, the thickness of the CF, and the dielectric constant of the CF. In general, the thickness of the liquid crystal layer is 5 to 30 microns, the dielectric constant of liquid crystal is 1 to 10, and the film thickness of dyed C and F is 1 to 2 microns. Although this dielectric constant varies depending on the material of the dyed layer, it is 1 to 10. It is 10 microns.

Therefore, the rate of increase in drive voltage is several tens of percent.

On the other hand, when displaying a large number of pixels by time-division driving, the duty ratio increases and it is necessary to increase the driving voltage pulse.

However, due to the withstand voltage limit of the liquid crystal driving IC, (CLC10 CF
/Ccp) times the driving voltage pulse could not be applied. For this reason, the LCD display on/off controller 1-
There was a problem that the last part got worse.

In the case of 2), the dyed layer is an organic film such as gelatin and is soft, so it was not possible to directly form a transparent electrode on the dyed layer. This is due to the pressure caused by rubbing used in the alignment process during the manufacture of liquid crystal panels, which causes cracks in the transparent electrodes.

Furthermore, in order to solve this problem, a method is also used in which a hard protective film is formed on the dyed layer and then a transparent electrode is formed. However, the drawback of this method is that the substrate (the transparent electrode substrate on which the CF is formed) must be heated for 20 minutes to produce the transparent electrode.
This is something that can only be done down to around 0°C. For this reason, crystallization of ITO (indium tin oxide alloy) generally does not proceed, resulting in a high specific resistance, and electrolytic corrosion of the ITO wiring in the liquid crystal panel is likely to occur, resulting in an unreliable liquid crystal panel. There was a problem that it was easy to do.

[Means to solve the problem]

A transparent electrode is formed in a predetermined pattern on a transparent substrate,
To obtain a CF having an organic pigment layer on the transparent electrode, the substrate and the current-carrying electrode are immersed in a solution in which a water-insoluble organic pigment is solubilized in a micellar aqueous solution of a surfactant, and the transparent electrode is identified. By applying electricity between the pattern and the current-carrying electrode, electrode oxidation of micelles is performed on the transparent electrode, and organic pigment molecules are precipitated on the transparent electrode. The above-mentioned problems are solved by CF, which is characterized in that it is formed by repeating patterns of pigment and other transparent electrodes.

The structure of the liquid crystal CF of the present invention is such that ITO or a tin oxide alloy is formed as a transparent electrode on a transparent substrate such as glass or quartz. ITO and tin oxide alloys are produced by sputter CVD.
Since the film is formed at a high temperature of 300°C or higher, the specific resistance is reduced and the chemical stability is increased.

Furthermore, unlike the dyeing method, since the organic pigment layer is directly formed on the transparent electrode, there is no need for a resin layer that acts as a binder compared to the dyeing layer produced by the dyeing method, so the film thickness can be made thinner. The thickness of the organic pigment layer is determined depending on the type of organic pigment and the intended use of CF, but it is between 0.05 and 0.05.
．． Sufficient spectral characteristics can be obtained at 5 microns. The dielectric constant of organic pigments is generally 1 to 10, which is almost the same as the dielectric constant of dyed CF, so it is possible to lower the rate of increase in driving voltage, thereby preventing deterioration of the on/off contrast of the liquid crystal display. Can be done.

Next, the general manufacturing process of the CF of the present invention will be described.

The production of CF of the present invention involves preparing a micellar aqueous solution using a surfactant, dispersing and suspending an organic pigment in this aqueous solution, and stirring for a long time to slowly release molecules from the organic pigment. is gradually solubilized into micelles to create a micellar aqueous solution of organic pigment.

The surfactant has a low micelle degree limit and easily forms micelles. Preferably, it becomes positively charged through oxidation and repels the positive electrode, causing the micelles to collapse and transfer the solubilized organic pigment molecules to the positive electrode. From this point of view, surfactants having a metallocene group (Ni, Ru, Os, Pd, etc.) as the hydrophobic end group of the molecule are preferable.
Also, the concentration may be micellar (moderate or higher).

It is desirable that the organic pigment molecules to be dispersed and suspended be as finely pulverized as possible; however, the smaller the particle size, the smaller the particle size, the shorter the dissolution time into micelles.

The aqueous solution is stirred for about 10 to 200 hours, and the molecules that are slightly dissolved from the organic pigment are gradually dissolved into the micelles and saturated. Examples of organic pigments include nitro pigments, nitroso pigments, acid dye lakes, basic dye lakes, mordant dye lakes, chiazo pigments, azo complex salt pigments, condensed azo pigments, benzimidacylon pigments, phthalocyanine pigments, anthraquinone pigments, thioindigo pigments, and beryinone pigments. , perylene pigments, quinacridone pigments, dioxazine pigments, and quinophthalone pigments.

Furthermore, 0.01 to 5M of 11BR, L+2304, etc. is added as a supporting electrolyte.

As a supporting electrolyte, this aqueous solution is allowed to stand and the supernatant is removed, or insoluble matter is separated by centrifugation.

A transparent substrate having transparent electrodes formed in a predetermined pattern and a counter electrode are immersed in this solution. As a transparent electrode, C
Tin oxide alloy formed by VD method, sputtering method, etc., IT
Examples include O1 zinc oxide.

Next, a positive potential is applied to the transparent electrode relative to the counter electrode in a deoxidized atmosphere to reach the micelle destruction potential, which destroys the micelles through electrolytic oxidation and precipitates supersaturated organic pigment molecules on the transparent electrode. be.

The electrolytic potential is determined by the combination of surfactant and organic pigment molecules. Furthermore, stirring the solution during electrolysis increases the rate of precipitation of pigment molecules, which is effective.

The reason for performing electrolysis in an oxygen-free atmosphere is to prevent decomposition of the reduction product of the surfactant.

Next, a detailed explanation will be given using examples.

(Example 1) ITO film was sputtered on soda glass at 300°C.
The film is formed to a thickness of 1000A while heating the substrate. This is patterned into a predetermined pattern using photolithography. A predetermined ITO pattern and a power supply are connected, and a platinum plate as a counter electrode is also immersed in a micelle aqueous solution.

The micelle concentrate used ferrocenyl PEG (manufactured by Dojin Kagaku) as a surfactant having a metallocene group. Prepare 100ml of a 2mM aqueous solution of this surfactant, and add 02M as a supporting electrolyte.

B was added as an organic pigment, and 250 μm of Cromophthal A3B (manufactured by Ciba Geigy, red) as an anthraquinone pigment was added and stirred by ultrasonic waves for 15 minutes to suspend the pigment molecules in the aqueous solution.

Next, this suspension was vigorously stirred for about 30 hours, and then allowed to stand for 24 hours, after which the supernatant liquid was collected to obtain the above-mentioned micelle aqueous solution.

A voltage was applied using an ITO pattern as a positive electrode, a platinum plate as a negative electrode, and a saturated calomel electrode as a reference electrode.

The electrolytic potential was set to +0°5 from the reference electrode, and electrolysis was carried out for 30 minutes while stirring the solution.

Through this operation, a red film of Cromophthal A3B was formed with a thickness of 4500A. Similarly, using ferrocenyl PEG (manufactured by Dojin Kagaku) as a surfactant, 100 ml of a 2 mM aqueous solution of this surfactant was prepared,
Furthermore, 0°2M glue, B, was added as a supporting electrolyte, and an anthraquinone pigment, indanthrone blue (Pgment Blue 60, Cl) was added as a blue organic pigment.
69800) was added thereto and stirred by ultrasonic waves for 15 minutes to suspend the pigment molecules in the aqueous solution.

Next, this suspension was stirred vigorously for about 30 hours, and then left to stand for 24 hours. A micellar aqueous solution was made by collecting the supernatant water from the waterfall. Platinum plate, reference electrode and ITO
The substrate was soaked. A potential of +06 V was applied to a predetermined ITO pattern other than the above-mentioned To pattern for 30 minutes based on the reference electrode.

As a result, a blue coating was formed with a thickness of 1500 mm.

Next, using the same method, Heliogen Green was added as a metal phthalocyanine pigment as a green organic pigment.
L19140 (manufactured by BASF) was suspended in 300 μm of the same micelle solution as above in the same manner.

This suspension was then vigorously stirred for approximately 30 hours, followed by 24 hours.
After standing for a period of time, the supernatant liquid was collected to prepare a micelle aqueous solution. The platinum plate, the reference electrode, and the above-mentioned ITO substrate were immersed in this micelle aqueous solution. A green metal phthalocyanine film with a thickness of 300 OA was formed by applying a potential of +0.5 µ based on the reference electrode for 40 minutes to the ITO pattern on which the red and blue organic pigment layers were not formed.

In the above manner, CFs formed on red, blue, and green organic pigment coatings or predetermined I"r'0 patterns were obtained. Since these pigment layers do not have a resin binder layer, C
It showed a color density of 1-minute as F.

Using this CF as one transparent substrate, a liquid crystal panel with a thickness of 10 μm was created. A 64 Hg sine wave was applied to the red pixels, and the effective applied voltage of the liquid crystal panel and the transmitted light intensity of the liquid crystal panel were examined.

For comparison, we created a liquid crystal panel using CF by the relief dyeing method and a liquid crystal panel without a CF layer, and examined the effective applied voltage and transmission intensity of the liquid crystal panel.
h A photosensitive gelatin layer with a thickness of 1.5 μm is formed on a glass substrate having a polar pattern by a spin coding method,
It is dyed red with acid dye. 1.5. +
The film thickness of zrrt is determined in advance in order to obtain a color density that is approximately equivalent to that of the red layer of the CF of the present invention.

The above results are shown in FIG. The horizontal axis shows the effective applied voltage, and the vertical axis shows the transmittance. To facilitate comparison, let the transmittance when the applied voltage is OV be O, and let the light transmittance of each panel be 100, and show the relationship between the voltage and the transmittance. As a result of the present invention, the threshold value 41 is increased by about 5% compared to the case 42 without the CF layer, but the threshold value is significantly improved compared to the case 43 when the CF by the relief staining method is used. Seen,
It is sufficiently practical.

〔Effect of the invention〕

As described above, the CF of the present invention is advantageous in terms of mass production compared to the conventional relief dyeing CF process because the photolithography process is removed. or,
The problem of increase in driving voltage when forming a CF layer on the electrode is as follows.
It is extremely small and allows conventional ICs to be used within their withstanding voltage range. Furthermore, since the transparent electrode layer is under the CF, sufficient heating can be carried out during the formation of the transparent electrode, making it possible to provide a liquid crystal panel with low resistivity and high fidelity through crystallization. .

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a liquid crystal panel using the CF of the present invention. FIG. 2 is a cross-sectional view of a liquid crystal panel using conventional relief dyed CF. FIG. 3 is an equivalent circuit diagram of a liquid crystal panel using CF. Figure 4 is a diagram showing the relationship between the effective voltage applied to a liquid crystal panel and the light transmission of the liquid crystal panel. Transparent substrate Transparent electrode sealing material Liquid crystal organic pigment layer Transparent substrate Transparent electrode sealing material Liquid crystal dyed layer Relationship when using the CF of the present invention Relationship when there is no CF Relief dyeing When using CF

Claims (1)

[Claims] A transparent electrode is formed in a predetermined pattern on a transparent substrate,
To obtain a color filter having an organic pigment layer on the transparent electrode, the substrate and the current-carrying electrode are immersed in a solution in which a water-insoluble organic pigment is solubilized in a micellar aqueous solution of a surfactant. By applying electricity between a specific pattern and a current-carrying electrode, electrode oxidation of micelles is performed on the transparent electrode, and organic pigment molecules are deposited on the transparent electrode. A color filter characterized in that it is formed by repeating patterns of organic pigments and other transparent electrodes.